Pantograph



Feb. 18, 1958 l..A VAI-.ois

PANTOGRAPH Filed Nov. `4. 1955 The present invention relates to a drafting instrument and more particularly to a draftinginstrument .of the pantograph type to produce an accurate reproductive relation betweenv the tracer and the marker within a wide range of various adjustments for either enlargement or reduction.

Known pantographs arebased on the principle of a deformable parallelogramy and require at least two adjustments for setting the scale to which a drawing is to be reproduced.

Moreover, pantographs of the ldeformable parallelogram type usually lay fiat on the drawing board and are therefore very cumbersome to utilize.

Accordingly, the general object. of the present invention is the provision of a drafting instrument of the pantograph type which is based on a' new principle of yoperation whereby only one Vadjustment is required for setting the scale of reduction or enlargement of the drawings to be reproduced. i v

Another important object of the present invention is the provision of a pantograph in which all the articulated members extend in a plane perpendicular to the plane of the drawing board thereby taking a minimum of space on said drawing board.

Yet vanother important object ofthe present invention is the provision of apantographbased on the principle of deformable similar triangles having a common apex and parallel bases andY in which the scale of enlargement or reductionmay be changed by'simply varying the position of the base of one'of the triangles.

Still another important object of the present invention is the provision, in a pantograph of the character described, of friction means engaging the drawing table, which will have a friction value substantially greater than the sum of the frictions exerted by the various movable elements. of the pantog'raphso a'sto provide uniform ease of operation'of the pntg-rph in'an'y direction 4ofl movement of the same.

Still another important object of the present invention is the provision of a pivot for said pantograph, which may be adjustably mounted on the drawing board in the most suitable position for the operator.

Another important object of the present invention is the provision of a pantograph of the character described which is simple and relatively inexpensive to manufacture and which will give prolonged service.

The foregoing and other important objects of the present invention will become more apparent during the following disclosure and by referring to the drawings in which:

Figure 1 is a perspective view of the pantograph according to the invention in operative position on a drawing board;

Figure 2 is an elevation of the pantograph;

Figure 3 is a section taken through the rigid bar of the pantograph and through one of the stylus carrying members;

Figure 4 is a longitudinal section'of the free end of the rigid bar and of the friction disc pivoted thereon; and` Figure 5 is an kelevation partially in section of the means for pivotally and slidably mounting the rigid bar of the pantograph according to the invention.

Referring now more particularly to the drawings in which like reference characters indicate like elements'V throughout, the letter A indicates a drawing board or the like flat surface on one edge of which is secured a. bracket 1 by means of screws 2. The bracket 1 has aV flange 3 through which passes a bolt 4 threadedly engagr ing a clamping knob 5 which serves to clamp in adjusted position a base 6 having a longitudinal slot 7 engaged, by bolt 4. The base 6 may thus be pivotally as well asA longitudinally adjusted. On the outer end of the base 6' to the drawing board A.

One end of a rigid bar 11, preferably of square crosssection, is supported by and is longitudinally slidable',Y within the guiding member 10. The other end of the,

rigid straight bar 11 mounts a friction disc 12 having a Hat Contact area adapted to rest on the drawing board- A. The friction disc 12 is secured at the end of an arm 13 depending from a head 14 having a spindle 15 rotatable within an axial bore made at the free end of thel rigid bar 11. Thus the disc 12 may rotate in a plane perpendicular to the longitudinal axis of the bar 11.

A stylus carrying member 16 is rigidly secured to the bar 11 near the friction disk 12 and consists of two laterally extending, vertically spaced ears 17 bored to receive a stylus such as the tracing stylus 18.

Another stylus carrying member 19 is mountedon the` rigid bar 11 and is freely slidable longitudinally of the same. bular sleeve having a square inner bore adapted to have a slidingt on the bar 11. Two lateral ears 20 projectA from one side of the member 19 and have registering holes to receive a stylus such as the marking stylus 21.V The latter may be in the form of an automatic pencil; the lead 22'of which may be adjustably fed by the coulv trol knob 23 which also acts as a suitable weight to provideclear writing.

The first leg of the pantograph is constituted by two spaced parallel straight bars 24 pivotally connected atV their lower ends at 26 to upstanding ears 27 mounted on; the guiding member 10. The upper ends of the bars 24.'r

are pivotally connected at 28 to one end of the second leg 29of the pantograph. The other end of the straight leg 29 is pivotally connected at 30 to two upstanding ears 31 secured to the bar 11 in alignment with the stylus carrying ears 17.

The third straight leg 32 of the pantograph is pivotally connected to the stylus carrying member 19 by means of pivot pin 33 passing through upstanding ears 34 secured to the stylus carrying member 19. The third leg 32 is provided with a plurality of holes 35 each one of which is adapted to register with one of a plurality of pairs of registering holes 36 made in the bars 24 of the first leg of the pantograph for receiving a removable pivot pin 37.

The pin 37 may be shifted along the legs 24 and 32 to cooperate with different holes 35 and 36 in order to vary the ratios of enlargement or reduction as the case may be.

The holes 35 and 36 are so located along legs 24 and 32 as to provide a progressing ratio of enlargement or reduction in predetermined increments and such that the leg 32 will be parallel to leg 29 when a hole 35 registers with the corresponding pair of holes 36. To facilitate adjustment of the pantograph, the corresponding holes Patented Feb. 18, 1958;

The stylus carrying member 19 consists in a tufV 35 and 36 are preferably marked with the value of the reduction or enlargement ratio obtained when sai-d holes are in register.

In order to obtain parallelism between legs 29 and 32, the distance between any one hole 3S and pivot 33 over the length of leg 29 must be proportional to the distance between pivots 26 and the pair of holes 36 corresponding to said one hole 35, over the total length of leg 24.

The device must also be so constructed that the pivots 26, 33 and 30 will lie in a plane parallel to that of the drafting table A, and styli 22 and 18 will lie in a plane passing through pin 8, the pivotal point of the bar 11, said styli 22 and 18 being movable in said plane when accomplishing radial movements with respect to pin 8.

The third leg 32 always being maintained parallel toV the second leg 29, the ratio of the distance of the stylus carrying member 19 to the pivot member 8 over the distance of the stylus carrying member 16 to pivot member 8 will always be constant and therefore the scale of reduction or enlargement of the reproduced drawing will always be maintained constant for a predetermined adjustment of the pantograph by means of pivot pin 37 and holes 35 and 36.

It is understood that while Figure 1 shows a pantograph adapted to reduce a drawing the same may be used for enlarging a drawing by simply interchanging the marking and tracing styli 21 and 18.

While the pantograph, according to the invention, in the embodiment illustrated, may be adjusted step by step for changing the scale of reproduction of the same it may be understood that means may be provided for varying said adjustment in a continuous manner.

The legs 24, 29 and 32 of the pantograph, according to the invention, extend in a plane perpendicular to the drawing board A and therefore will take up a minimum of horizontal space on said board. This pantograph is, therefore, much less cumbersome than the usual pantographs known in the art, which :are adapted to lie at on the drawing board.

It will be understood that the frictional resistance exerted by the sldable stylus carrying member 19 will vary according to the position of the rigid bar 11 relatively to the guiding member 10, therefore, the friction disk 12, by adding a constant frictional resistance substantially greater than the above mentioned variable resistance, will provide a substantially uniform overall frictional resistance thereby facilitating operation of the pantograph according to the invention.

It will be noted that the mounting of the pivot pin 8 on the drawing board, may be easily adjusted so as to i locate said pivot member 8 at the most convenient position for the user of the pantograph and depending on the size of the drawings to be reproduced.

For certain purposes, as, for instance, when the space available above the drawing board is limited, thev construction ofthe pantograph, according to the invention, may be modied such that the pivots 26, 33 and 30 will be displaced transversely and/or longitudinally with re spect to the pvot pin 8 and styli 22 and 18, provided that the pivots 26, 33 and 30 remain in a plane parallel to the plane of the `drafting table A, that the distance between pivots 26 and 33 remains equal to the distance between pivot pin 8 and stylus 22, and that the distance between pivots 26 and 30 remains equal to the distance between pivot pin 8 and stylus 18.

While preferred embodiments according to the present invention have been illustrated and described, it is understood that various modications may be resorted to without departing from the spirit and scope of the appended claims.

I claim:

1. A drafting instrument of the character described comprising an upright pivot member adapted to be mounted on a drawing board or the like, a channelshaped guiding member pivoted on said pivot member, a rigid bar of a cross-section fitting said channel-shaped member, said bar sldable longitudinally through said guiding member, a first stylus carrying member movable longitudinally of said bar, a second stylus carrying member secured to said bar, means for moving said rst stylus carrying member longitudinally of said bar according to a predetermined constant ratio with respect to the longitudinal movement of said bar through said guiding member, and a drawing board engaging plate mounted at the end of said rigid bar remote from said pivot member and supporting said end of said rigid bar, said plate being pivotable about the longitudinal axis of said bar in a plane perpendicular to said bar.

2. A drafting instrument as claimed in claim 1, said plate being in the form of a disc.

References Cited in the le of this patent UNITED STATES PATENTS 836,221 Shaker Nov. 20, 1906 1,079,910 Anderson Nov. 25, 1913 1,351,211 Keller Aug. 31, 1920 1,857,285 Phillips May 10, 1932 2,496,781 Eichmann Feb. 7, 1950 2,627,658 Green Feb. 10, 1953 2,636,271 Valois Apr. 28, 1953 2,645,016 Wrobel July 14, 1953 2,739,511 Rafart Mar. 27, 1956 2,742,823 Compton Apr. 24, 1956 2,766,529 Dwyer Oct. 16, 1956 FOREIGN PATENTS 7,074 France May 10, 1840 442,038 Italy Nov. 15. 1948 

